The selection of relevant information from cluttered environments for further processing is one of the most fundamental cognitive abilities for guiding behavior. This becomes strikingly clear when attentional selection mechanisms fail, such as in individuals afflicted with ADHD, visuospatial hemineglect that is often observed after stroke, and schizophrenia. Converging evidence from physiology and functional brain imaging studies reveals that attentional selection occurs at multiple stages along the visual pathway. E.g. neural responses are modulated by spatially directed attention to a target location as early as in the lateral geniculate nucleus and at each successive visual processing stage. These modulatory influences appear to be generated by a network of higher-order areas in frontal and parietal cortex including the frontal eye fields and lateral intraparietal area (LIP). While much effort has been made towards an understanding of attentional mechanisms at the cortical level, the functional role of subcortical areas is poorly defined. There is evidence from human and macaque lesion studies that a large thalamic nucleus, the pulvinar, plays an important role in the selection process. The pulvinar is widely connected with fronto-parietal and visual cortex and is thus well positioned to influence communication across the cortex. However, very few physiology studies probing pulvinar activity during attentional selection tasks have been performed. The goal of the proposed research is to characterize attentional function in the pulvinar (SA #1) and to characterize how the pulvinar and cortex interact during attentional selection (SA #2). The central hypothesis is that the pulvinar coordinates activity in cortical areas, in order to regulate information transmission according to attentional requirements. To test this hypothesis, we will simultaneously record neural activity in the pulvinar and cortical area LIP, while monkeys perform a selective attention task. The proposed research is aimed at advancing our understanding of the neural mechanisms and the network interactions that mediate attentional functions in the primate brain. Progress in understanding the basic mechanisms of selective attention is a first necessary step in developing effective treatment strategies for attentional deficits. PUBLIC HEALTH RELEVANCE: This research is relevant to public health because it is expected to advance our understanding of neural mechanisms underlying selective attention, which is one of the most fundamental cognitive abilities for guiding behavior. This becomes strikingly clear when attentional selection mechanisms fail, such as in individuals afflicted with ADHD, visuo-spatial hemineglect that is often observed following stroke, and schizophrenia. Progress in understanding the basic mechanisms of selective attention is a first necessary step in developing effective treatment strategies for attentional deficits.